Android 5.1外置存储卡文件无法删除

5.1上遇到一个诡异的情况：

file.exists(); > true

file.canWrite(); > true

file.delete(); > false

-----------------------------------

设备/system/etc/permissions/platform.xml

<permission name="android.permission.READ_EXTERNAL_STORAGE" >
<group gid="sdcard_r" />
</permission>

<permission name="android.permission.WRITE_EXTERNAL_STORAGE" >
<group gid="sdcard_r" />
<group gid="sdcard_rw" />
</permission>

<permission name="android.permission.ACCESS_ALL_EXTERNAL_STORAGE" >
<group gid="sdcard_r" />
<group gid="sdcard_rw" />
<group gid="sdcard_all" />
</permission>

<permission name="android.permission.WRITE_MEDIA_STORAGE" >
<group gid="media_rw" />
</permission>

源码位置：

frameworks/base/data/etc/platform.xml

增加WRITE_EXTERNAL_STORAGE的group id：

--- a/frameworks/base/data/etc/platform.xml
+++ b/frameworks/base/data/etc/platform.xml
@@ -70,6 +70,8 @@
<permission name="android.permission.WRITE_EXTERNAL_STORAGE" >
<group gid="sdcard_r" />
<group gid="sdcard_rw" />
+ <group gid="sdcard_all" />
+ <group gid="media_rw" />
</permission>

实测有效。